New measurements of the ion content of evaporation-humidified air

Abstract

New measurements by electrical conductivity of the ion content of untreated room air humidified by evaporating liquid water in a closed container are presented. Large populations of the singly charged hydrated ions can be maintained in the container for an hour or more after the liquid water evaporation source is removed. The new results suggest that evaporation produces large populations of neutral molecular clusters of many water molecules, and that the neutral clusters dissociate to a small extent into ions that can be monitored by electrical conductivity using cells of a new design to monitor the temperature and humidity dependencies of the neutral cluster populations. Data are presented showing ion population function versus saturation ratio (fractional relative humidity) and time at near-ambient temperatures. Ion population is very dependent on the saturation ratio and time of contact of the vapor with liquid water. This strong dependence impacts accepted electrostatic and insulator theories. Data also are presented from experiments in which ion content was measured in fully saturated moist air at temperatures to 50 °C, where the air was humidified by steam and ion populations in excess of 109/cm3 were observed.